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<head>
    <meta charset="UTF-8">
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    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .big {
            border: 1px solidb black;
            width: 350px;
        }

        h1 {
            background-color: black;
            color: white;
            margin: 0px;
            line-height: 80px;
            text-align: center;
        }
       
        p,
        h4 {
            padding: 10px;
        }

        p {
            border-bottom: double 2px crimson;
            padding-bottom: 10px;
        }
         
        .big {
            background-color: blanchedalmond;
        }
    </style>
</head>
<body>
    <div class="big">
        <h1>盒子模型练习</h1>
        <div class="big1">
            <h4>第一行小标题</h4>
            <p>第二行，内容文本</p>
            <h4>第一行小标题</h4>
            <p>第二行，内容文本</p>
            <h4>第一行小标题</h4>
            <p>第二行，内容文本</p>
        </div>
    </div>
</body>
</html>